Twilight Information for Today

When the sun is only a few degrees below the horizon, for a short time at the beginning and end of each day, the lower atmosphere is illuminated depsite not being directly visble to the sun. This time is known as twilight and occurs due to the scattering of sunlight in the upper atmosphere. Twilight is divided into three intervals as seen in the figure below, each of which is defined by the angle the centre of the sun is below the horizon. The observation of astronomical objects can usually occur from astronomical twilight and onwards into the night.